If you look in the Unix System Services User's Guide manual, you will find the syntax for the OGET command. The syntax explicitly states that having parentheses after the data set name is giving a PDS member name. There is no way to use OGET to reference a relative generation, period.

You will have to do an OGET into a data set, then use an IEBGENER (or your choice) step to copy the data set to the relative generation of the GDG.

Henrique, this Rexx will create a new generation of FILE.MYGDG. It will ignore data sets with HLQ FILE.MYGDG that are not part of the GDG. It will not handle the case of wrapping (i.e., going from G9999V00 to G0001V00). I do not know Unix, but perhaps you will not find it difficult to adapt to your needs.